UBI: print media information earlier

Print information about logicale eraseblock size, sub-page
size and so on at early stage, befor an attempt to attach
the MTD device was made. This is more convenient to do so
because the attempt to attach may fail, and the information
is never printed then.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>